Basically, the 2G/2.5G old network is a synchronous network and the 3G new network is an asynchronous network. Since different protocols and subscriber profiles are used in the old network and the new network, internetwork messages are not matched one to one.
In a state where the old network and the new network have been individually built, if network interworking is embodied by using a gateway, a lot of expenses are incurred due to double system investment. In addition to the huge expenses, only a part of functions which can perform mutual message matching can be interworked through a message transformation process of the gateway due to mismatching between the old network and the new network. That is, most of the major functions cannot be interworked. Even if functions of nodes of each network are modified and/or added and a very complicated message flow is generated for internetwork message interworking using the gateway, it not only results in huge expenses for modification and/or addition of the functions of the nodes of each network, but also complicates a message communication process for interworking between the nodes much more than a general communication process of an independent network. In the worst case, the complicated process may generate service failure due to deterioration of communication quality
One of the examples will now be suggested in relation to call forwarding.
FIG. 1 is a flowchart showing a call forwarding method in the 2.5G (or 2G) old network.
In a state where a subscriber reception mobile terminal (not shown) has accessed a corresponding mobile switching center (T-MSC) 11, a location registration procedure has been finished according to an old network protocol to register locations of the T-MSC 11 and a corresponding home location register (2G HLR) 12, and thus reception trigger information has been set up in the T-MSC 11. In the old network, the reception trigger information is set up only for call forwarding subscribers during the location registration procedure of the 2G HLR 12 and the T-MSC 11.
On the aforementioned assumptions, if a subscriber origination terminal (not shown) accesses a corresponding mobile switching center (O-MSC) 13 (to communicate with the reception mobile terminal), the O-MSC 13 requests location information of the reception mobile terminal, namely reception information to the 2G HLR 12 (S101), and thus the 2G HLR 12 requests routing to the T-MSC 11 which the reception mobile terminal has accessed (S102).
The T-MSC 11 provides temporary local directory number (TLDN) information of the reception mobile terminal to the 2G HLR 12 as the routing information in response to the routing request (S103), and the 2G HLR 12 provides the TLDN to the O-MSC 13 in response to the location request of S101 (S104), thereby forming a call path between the O-MSC 13 and the T-MSC 11(Isup) (S105).
Thereafter, the T-MSC 11 performs signaling for reception to the reception mobile terminal. Here, if the reception is not successful, the T-MSC 11 performs two operations on the basis of the trigger information and/or call forwarding information of the reception mobile terminal: the T-MSC 11 requests redirection to the O-MSC 13 (S106-1) or directly makes a transfer to number request (TTNR) to a corresponding HLR on the basis of the known call forwarding information (S106-2).
At the step of S106-1, the O-MSC 13 requests call switching information to the 2G HLR 12(TTNR) (S107), and the 2G HLR 12 provides the call switching information, namely call forwarding information to the O-MSC 13 in response to the request (S108).
The procedure of S101 to 105 is repeated among the O-MSC 13, a new HLR and a new T-MSC on the basis of the call forwarding information to form a call path between the O-MSC 13 and the T-MSC for call forwarding, thereby finishing reception (S109).
FIG. 2 is a flowchart showing a call forwarding method in the 3G new network.
In a state where a subscriber reception mobile terminal (not shown) has accessed a corresponding T-MSC 21, a location registration procedure has been finished according to a new network protocol to register locations of the T-MSC 21 and a corresponding 3G HLR 22, and thus forwarding data have been transmitted from the 3G HLR 22 to the T-MSC 21 and stored in the T-MSC 21. In the new network, the forwarding data are stored only for call forwarding subscribers during the location registration procedure of the 3G HLR 22 and the T-MSC 21.
On the aforementioned assumptions, if a subscriber origination terminal (not shown) accesses a corresponding O-MSC 23 (to communicate with the reception mobile terminal), the O-MSC 23 requests location information of the reception-mobile terminal, namely reception information to the 3G HLR 22 (SRI(Send Routing Information))(S201), and thus the 3G HLR 22 requests routing number to the T-MSC 21 which the reception mobile terminal has accessed(PRN(Provide Routing Number)) (S202).
The T-MSC 21 provides mobile station roaming number (MSRN) information to the 3G HLR 22 as the routing information in response to the request (S203), and the 3G HLR 22 provides the MSRN to the O-MSC 23 in response to the request(SRI) of S201(SRI_Ack) (S204), thereby forming a call path between the O-MSC 23 and the T-MSC 21(Isup) (S205).
Thereafter, the T-MSC 21 performs signaling for reception to the reception mobile terminal. Here, if the reception is not successful, the T-MSC 21 performs two operations on the basis of the stored forwarding information: when a subscriber of the forwarding information is for example, a foreign network subscriber, the T-MSC 21 provides the stored forwarding information to the O-MSC 23 to perform the succeeding reception process (RCH; resume call handling) through a corresponding gateway (not shown) (S206-1), performs the procedure of S101 (even when the RCH is converted by the gateway, namely RCH<−>Redirection Request, not LOC but TTNR is performed on the O-MSC) to S105 between the origination party and the reception party to form a call path between the O-MSC 13 and a corresponding T-MSC (not shown) for call forwarding, and finishes reception; and when a subscriber prefix of the forwarding information indicates a local network subscriber, the T-MSC 21 performs S201 on a corresponding JLR (not shown), sequentially performs the procedure of S202 to S205 to form a call path between the O-MSC 23 and a corresponding T-MSC (not shown) for call forwarding, and finishes reception (S206-2).
The RCH of S206-1 is determined according to optimal routing(OR) capability of the O-MSC, the HLR and the T-MSC. There, the T-MSC determines whether to transmit the RCH to the O-MSC. Here, when an operator sets up that the RCH is not performed in O-MSC signal point as in S206-2, the call is setup in a home HLR 24 of a call switching number according to the send routing information (SRI).
As described above with reference to FIGS. 1 and 2, the old network which is a synchronous network and the new network which is an asynchronous network use different protocols. While the HLR manages the call forwarding information and the corresponding MSC sets up the trigger information in the old network, the HLR directly provides the call forwarding information to the corresponding MSC during the location registration procedure and the MSC stores and manages the information in the new network. Accordingly, when the old network and the new network have been individually built, if the two networks are intended to be interworked for call forwarding through the gateway, following problems may occur as shown in FIG. 3.
FIG. 3 is a flowchart showing problems which may be generated when the old network and the new network which have been individually built are intended to be interworked for call forwarding through the gateway.
When a new network subscriber mobile terminal (3G MS) which has accessed a 2G old T-MSC 32 moves and accesses a 2G new T-MSC 31, the 2G new T-MSC 31 requests location registration to a corresponding 2G HLR 35(Registration Notification; RegNot.) according to a location registration procedure of the old network (S301). Because the 2G HLR 35 does not have subscriber information of the 3G MS, the 2G HLR 35 notifies the 2G new T-MSC 31 that the 3G MS is not its subscriber in response to the request (S302). Here, if the 2G new T-MSC 31 is provided with a roaming function, it request location registration to a gateway 33 in the same manner as S301(RegNot.) (S303).
The gateway 33 transforms the requested 2G message(RegNot.), into a corresponding 3G message(UpdateLoc), and requests location update to a corresponding 3G HLR 34 of the new network (S304). The 3G HLR 34 transmits a location cancel request message(CancLoc) to the gateway 33 so that it can be transmitted to the 2G old T-MSC 32 which the 3G MS belonged to before the movement (S305), and the gateway 33 transforms the 3G message(CancLoc) into a corresponding 2G message(RegCan) and transmits it to the 2G old T-MSC 32 (S306). When the 2G old T-MSC 32 responds to the message(regcan_Ack) (S307), the gateway 33 transforms the response message(regcan_Ack) into a 3G message(canc_Loc_Ack), and transmits it to the 3G HLR 34 in response to S305 (S308).
Here, the 3G HLR 34 transmits subscriber information including call switching information for call forwarding to the gateway 33 in response to the location update message(UpdateLoc) of S304 so that it can be transmitted to the 2G new T-MSC 31 which 3G MS currently belongs to(Insert Sub Data) (S309). When receiving the response from the gateway 33 (S310), the 3G HLR 34 transmits the location update message(UpdateLoc) to the gateway 33 so that it can be transmitted to the 2G new T-MSC 31 which the 3G MS currently belongs to (S311), and the gateway 33 transforms the 3G message(UpdataLoc) into a 2G message(Regnot_ack) and transmits it to the 2G new T-MSC 31 in response to S303 (S312). Here, the 2G message(Regnot_ack) cannot transmit the call switching information for call forwarding defined in 3G, and thus fails to transmit the trigger information which is a procedure of 2G. Although the location registration procedure is finished, the 2G new T-MSC 31 does not have the call switching information of 3G and the trigger information of 2G. As a result, the call forwarding service cannot be provided through the 2G new T-MSC 31 which the 3G MS currently belongs to.
When the new network and the old network have been individually built, if the new network and the old network are intended to be interworked by using the gateway, they are not interworked because the internetwork messages cannot be matched one to one due to different protocols and subscriber profiles. The interworking failure in call forwarding was explained above, but there are still potential problems, such as service failures in basic calls, short messages, etc., and complication of the message communication.